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v twin 20hp not running right

#1

J

jimmy40

i have a 20 hp v twin cylinder that is giving me issues. I consider myself pretty good with mower engines but I am lost now. it runs good on half chock but stays at high idle and doesn't slow back down. it has a little miss here in there. if I take it off chock it will idle good but at high idle it hunts bad almost to a point of dying. what I have done so far, rebuilt carb, all new fuel lines and a new fuel pump and gas tank. new plugs and set valves. there is no air mixture screw on the carb, that would be what I would adjust now if it had one. can anyone steer me towards something I have missed?


#2

M

mechanic mark

Post model number from under seat as well as all numbers from engine so we can help you out. Fresh high octane gas, check air & fuel filters for replacement, take a look at oil, if black change oil & filter. First check for gas in oil by smelling dipstick for gas.

Results operators manual engine & parts list, valve adjustment specs. are on page 9 in operators manual. Check out pages 14 - 16 in illustrated parts list concerning main jet, your code number 0167 will be needed to locate correct part. Check out kit part number & see if it's the same kit you installed in carburetor.


#3

J

jimmy40

Thank you for replying, it is a model 407777-0167 E1. the mower is a Poulan pro PPR20H42ST not a craftsman, I put wrong manufacture in first request by accident. the Oil is fairly fresh and no gas in in it. All new fuel lines and filter, new air filter, new fuel tank all have been installed.


#4

S

shiftsuper175607

jimmy40 said:
i have a 20 hp v twin cylinder that is giving me issues. I consider myself pretty good with mower engines but I am lost now. it runs good on half chock but stays at high idle and doesn't slow back down. it has a little miss here in there. if I take it off chock it will idle good but at high idle it hunts bad almost to a point of dying. what I have done so far, rebuilt carb, all new fuel lines and a new fuel pump and gas tank. new plugs and set valves. there is no air mixture screw on the carb, that would be what I would adjust now if it had one. can anyone steer me towards something I have missed?
Click to expand...

When you put the carburetor back on you possibly got a linkage wrong or in a bind?

Have someone move the choke and throttle handles/linkages as you watch their movement and the plates on the carb.

Also...sometimes there is more than one hole for a linkage to go in...you can put it back in the wrong one(I've done that) See if there are other holes for the throttle linkage rod to go in.


#5

J

jimmy40

choke moves freely along with throttle linkage, only one hole on each side to go in. choke goes from full open to full close, runs best half way, but wont idle down, sprayed cleaner around carb while running to check for air leaks, no change in running so tells me no air leaks.


#6

S

shiftsuper175607

jimmy40 said:
choke moves freely along with throttle linkage, only one hole on each side to go in. choke goes from full open to full close, runs best half way, but wont idle down, sprayed cleaner around carb while running to check for air leaks, no change in running so tells me no air leaks.
Click to expand...

Does the throttle plate go closed? as it will not throttle down, it would seem the problem is there.


#7

J

jimmy40

throttle plate moves freely, I watch it as it starts to hunt, and is all moving. I can get it to idle down but it is very slow when going from wot to idle, takes 10 seconds are so. if I leave the choke off it will idle great and speeds up slowly then after say half throttle it starts hunting bad. put choke on half and the hunting stops but wont idle back down as it should. its almost as if either getting air from somewhere else or the fuel bowl is not keeping enough gas in it to maintain wot with out hunting.


#8

J

jimmy40

thank you for all the assistance, I plan to pull carb again today and go through it again.


#9

T

Tinkerer200

I can send you a Service Manual (Overhaul Manual) for your engine IF you like. Address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com


#10

J

jimmy40

thank you sir, I have the engine manual and have set all to the specs listed but still have the problem, I have carb off now and am in process of cleaning it again and inspecting it again then will reinstall and test again.


#11

J

jimmy40

I took the Carb apart again, this time I pulled the air butterfly rod, and found that a foam ( gasket) had disintergrated. I have several new foams but not sure which to use or how they go in, is a metal gasket need to go with it? would this cause my problem ( I think it could) does anyone have a break down on the Nikki 498751 266 1717-091 carb?


#12

B

bnwood

I am having almost the exact same issue with my 20hp (407777 0124 E1)

I found this link for the carb
http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb.asp
http://outdoorpowerinfo.com/repairs/briggs_intek_v-twin_carb2.asp


#13

J

jimmy40

The foam was causing my issue. Then I found spring bad on governor. It is running perfect again.


#14

T

Tinkerer200

You didn't post the code numbers so don't know age of engine NOR manual. First Service Manuals had incorrect valve adjustment instructions saying to adjust AT TDC later bulletin corrected to 1/4" down past TDC. High octane fuel will do you no good engine is not designed for it. Whenever carb is removed, Gov Static adjustment should be checked, reset.

Your symptoms indicate bad air leak OR bad carb passage blockage.

Walt Conner


#15

reynoldston

reynoldston

I have found through the years of repair that when a engine hunts you have low speed problem. Some where the low speed circuit is plugged inside the carburetor. It doesn't take much to plug it.


#16

J

jimmy40

The foam on butterfly shaft was causing my issue with hunting. After fixing that I found the spring on governor wouldn't allow to return to low idle properly. I have corrected both and all is good again. Thanks for all the help. And yes my valve are set to the latter of 1/4 past Tdc.


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